San Francisco
— Recent revelations indicate that past dumping of radioactive wastes at sea by US government agencies and private organizations may have been considerably more extensive than was earlier thought.

At the same time, federal officials admit that not nearly enough is known about the location and scope of such dumping or the danger that it now may pose.

Answers to these questions, now sought by congressional panels, could provide key direction for future disposal of nuclear waste.

While the United States halted such ocean dumping 10 years ago, resumption has not been ruled out. Other countries -- including Britain, Belgium, Switzerland, and the Netherlands -- have continued the practice. And Japan plans to begin dumping radioactive wastes in the northwest Pacific Ocean next year.

The Farallon Island dump site near here has been the focus of the controversy in recent years. It encompasses an area of at least 300 square miles located in a major shipping lane and commercial fishing area some 50 miles off San Francisco. Between 1946 and 1970, tens of thousands of barrels of "low-level" radioactive waste were dumped there as well as in other locations off the coasts of California, New Jersey, and Massachusetts.

Testifying before the US House of Representatives subcommittee on environment , energy, and natural resources this week, Nuclear Regulatory Commission (NRC) official Richard Cunningham said there were 27 such dump sites in US coastal waters. Environmental groups, however, have used the Freedom of Information Act and other investigative measures to determine that there were at least 50 of these sites.

Federal agencies, including the Environmental Protection Agency (EPA) and US Navy, in fact, have asked such private groups as the Committee to Bridge the Gap to provide them with information on nuclear dumping, said Daniel Hirsch of the Los Angeles-based Environmental Research Organization.

EPA assistant administrator David Hawkins told the congressional panel in San Francisco that the now-defunct Atomic Energy Commission (AEC), which was supposed to license such dumping, did not keep accurate records and that some of the records have been destroyed. While the EPA has been trying to find out more , Mr. Hawkins testified, its information "is neither comprehensive nor complete."

Three years ago, EPA scientists in a research submarine found and tested about 250 of the 50,000 or more barrels of radioactive materials in the Farallon Island area. About one-fourth of these were broken and leaking. While initial testing indicated no apparent environmental damage, Hawkins said, this was more "a matter of luck and not of planning" and in any case should "not in any sense be regarded as a clean bill of health."

Other scientists, including University of California biology Prof. W. Jackson Davis, have recently determined that radioactivity levels in the area of the barrels are far higher than "background" radiation (what would normally be found in the environment) or what could have resulted from earlier nuclear weapons testing fallout. Professor Davis and others are concerned that radioactive particles may be eaten by ocean organisms and work their way up the "food chain" to species of fish consumed by humans.

The US Department of Energy (DOE), successor to the AEC for some parts of radioactive waste control, apparently is even less certain than the EPA and NRC about the breadth and validity of its information on past ocean dumping. The department refused the congressional panel's request to appear before the San Francisco hearing.

Despite the longstanding controversy, the DOE, according to an unsigned statement released here, "is not prepared to present any new technical data at this time."

A recently revealed AEC report written in 1957 suggests that total at-sea radioactive waste could be 10 times greater than EPA estimates now show. Most waste was supposed to be dumped in 6,000 feet of water in specific locations. But according to this report, private ship captains contracted to do the dumping sometimes dropped their radioactive cargo elsewhere when encountering inclement weather or malfunctioning equipment.

Harold Ross, director of the nonprofit diving group called Project Tektite says his organization has found such barrels -- nearly all of which are corroded and spilling their contents -- fewer than 20 miles from San Francisco in 60 to 160 feet of water.

Even less is known about past military dumping of radioactive materials. There have been recent reports that the US Air Force may have dropped some materials from the air and that a spent nuclear reactor from the submarine Seawolf was sunk 120 miles off the coast of Delaware in 1959.

"We don't know what the military has dumped and where," said Rep. Paul McCloskey (R) of California. "The unlicensed [i.e., military] dumping may exceed the licensed dumping."

According to a recent issue of Science magazine, the Navy is considering scuttling old nuclear submarines (including their reactors) when they are decommissioned.

The congressional probe will continue when members reconvene after the Novem ber election. And it will focus in particular on military dumping. Hawkins promised to join the NRC and National Oceanic and Atmospheric Administration in regularly monitoring dump sites for possible environmental damage. The last such testing was done more than three years ago.